M32.9: Systemic lupus erythematosus, unspecified

The immune system protects the body from pathogens and foreign substances. The immune system can also destroy cells in the body that have pathologically changed. Some of the immune system’s antibodies can make pathogens and foreign substances visible to the immune system. Other antibodies attack pathogens or foreign substances directly.

Lupus involves the antibodies attacking the body’s own connective tissue. The connective tissue that is attacked may be in different parts of the body, for example in the skin and blood vessels. The antibodies cause inflammation in blood vessels, in particular. Blood vessels transport the blood from the heart to the different tissues and organs in the body, and back again. In so doing, they provide the tissue and organs with oxygen and nutrients, and remove waste substances. When blood vessels become inflamed so that they are damaged, organs can be damaged too. For example, if the blood vessels in a muscle are damaged, that muscle may be painful.

With lupus, the skin, joints and internal organs can be affected. Typical complaints include pain in the muscles and joints. The skin, for example of the face, may also turn red. The kidneys can also be affected. When the kidneys are affected they may no longer work properly. The kidneys also control blood pressure. So one can have high blood pressure when the kidneys are affected.